Several things to consider for them.
1) this is a new AD, Mike Bobinski left for GTech so their connection to the past isn't the driving force today (for better or worse)
2) Edmund Summers showed up on the list of names that was linked. The amount he was given was small, and the way it was presented doesn't even indicate if
Xavier/Mack had a direct involvement, it made it appear like it was an agent, not the university or a booster, however it may give the powers that be at X second thoughts about promoting from within; they may want a clean slate "just in case"
3) they have great fan support and are at or near the top of the Big East in terms of facilities, its a much more desirable job today than it was the last time they replaced a coach; they will have no shortcomings of people interested in the gig.
4) Pitino has been out the entire basketball season and everyone knew Mack was someone they would likely consider. If X's AD is worth his salt, he's already known who his primary replacements were going to be and if they would return the interest; I expect they'll have a replacement in order quickly.